Electronic discharge device



June 17, 1947. H. L. LOUDEN 2,422,427

A. l ELECTRONIC DISCHARGE DEVICE I Filed Jan. 21,` 1944 f4-{5.1m- "1 j 24 22 z5 Y 24 "75 I /6 (/5 l v J4 j* 1Z0 /f lnvenfbov:

Harry L. Louden,

Patented June 17,1947

ELECTRONIC DISCHARGE DEVICE Harry L. Londen, Cleveland, Ohio, assigner to General Electric Company, a corporation of New York Application January 21, 1944, Serial No. 519,112

(Cl. Z50-165) 4 Claims.

This invention relates to the activation of electrodes of electric discharge devices, and especially to activation effected by matter in vaporous or suspended form that is introduced or liberated into a discharge device envelope to come in contact with an electrode to be activated. The liberation of such matter may take place after the initial evacuation of the discharge envelope, and matter thus disseminated in the envelope may also serve the purpose of a getter to clean up residual gas or vapor and improve the vacuum. The invention is here explained with particular reference to its employment in the manufacture of a simple type of photocell having a cathode surfaced with an antimony and caseium combination; but it will be understood that it is applicable to other types of discharge devices, such as electron multipliers, for example. Likewise, it is applicable to .electrodes surfaced with other combinations besides antimony and caseium, such as bismuth and caseium, antimony and rubidium, or any useful combinations of vaporizable first group metal with metal f the fth group of the periodic system. Various features and advantages of the invention will be come apparent from the description of a species and form of embodiment, and from the drawings.

The single figure of the drawing shows a vertical longitudinal section through one form of photocell device, partly of vitreous construction, which conveniently embodies the invention.

A photocell device X is shown in the iigure as comprising a short vitreous or glass envelope tube I0 having its ends sealed by fusion to the margins of abutting annularly embossed discs or electrode headers II, I2 of sheet metal (such as chrome iron or Allegheny 55, as it is com'- mercially known), generally similar to those used for the ends of the tubular incandescent lamps commercially known as Lumiline lamps. The cathode header II which appears at the bottom in the figure carries a coaxial sheet metal cathode disc I3 (as of Nichrome or nickel) welded thereto and shown with its outer edge turned up toward the anode header I2. As shown, a glass appendix or exhaust tube I5 is attached or sealed by fusion to the outer side of the centrally apertured header II, substantially coaxial with its aperture and with a corresponding central opening I6 in the disc I 3. The anode header I2 which appears at the top in the figure is not apertured, but carries or embodies a central container I8 in which is a charge or pellet I9 which yields metallic caseium vapor under heat, such as a well-known mixture of caseium chromate with silicon as a reducing agent. Current connections 2B, 20 are shown welded to the headers II, I2.

As thus far described, the cell device X corresponds substantially to those heretofore manufactured. In accordance with the present invention, however. this device X differs importantly from the old cells just referred to as regards the container I8 for the caseium mixture, and associated features.

As shown in the gure, the end header I2 which carries the container IB has a reentrant, inward projecting disc-like central area 2I coaxial with the tube I0, and a sheet metal cover 22 of disc-like form coacts with this area 2I to enclose and contain the charge I9 between them. Accordingly, at least one of the disc-like parts 2|, 22 is recessed or dished to provide the required room. As here shown, the header wall area 2| is spherically recessed internally for this purpose, while the dished cover 22 is larger than the area 2| and has its margin 23 turned back on a bevel to extend outward and rearward toward the header I 2 around its area 2 I, somewhat like a pie-pan rim-the central area inside the rim 23 being shown flat'. 'I'he cover 22 may be spot-welded to the header II at the edge of the area 2l, at one or more points 24 in its circumference, so as to permit escape of matter outward from the periphery of the recess where the cover is unattached to the metal wall, as is necessary when the charge I9 in the container IB is heated and flashed. This allows escape not only of the alkali metal vapor formed by flashing the charge. I9, but also of getter vapor from a small charge 25 (such as a bar of metallic baium) which may be enclosed in the container I8 along with the charge I9, and may be heated, ilashed, and vaporized at the same time. The rim 23 serves to deflect back toward the header wall around the recessed and reentrant area, away from the cathode I5 and cathode header I I, the vapor and any solid matter or residue that may escape peripherally outward from between the parts 2|, 22. Thus the vapor is prevented from blowing directly on the cathode I3 and depositing there too heavily or unevenly, and solid particles escaping from the container I8 are caused to depositY on the header I2 and prevented altogether from reaching the cathode I5 to deposit therewhich would render the cell X practically useless.

In manufacturing the cell device X above described, the cathode disc I3 is welded to the header II and the tube I0 is sealed at one end to this header, the cathode disc I3 is surfaced with a thin coating of antimony thermally deposited thereon, the charges i9, 25 maybe put in place' and the cover 22 secured to the edge of the area 2'l over them (care being taken not to flash either of the charges I9, 25 in Welding on the cover 2l), and the header I2 is sealed to the end of the tube I0, the glass tube l5 being also sealed to the header ll. In its subsequent processing, the cell device X is baked and exhausted, and the charges I9, 25 are flashed by heating the header I2, as by means of a (hydrogen) gas torch or a high frequency coil, thus forming metallic caesium and barium vapors and liberating and introducing them from the container I 8 into the cell X, as already described. Concurrently, the cell X is cooled by air jet (s), except where thus heated. This results in deposition of condensed metallic caesium on the glass walls I Il and on the antimony-coated surface of the cathode I3, in amounts materially exceeding what is needed to unite or combine with the antimony. The cell X is then heated in an oven to a suicient temperature (such as some 225 C.) to revaporize the excess caesium and drive it out of the cell via the tube l5, after which the cell X is tipped or sealed off short from the tube l5 as indicated in dotted lines, leaving the resulting exhaust tip 26 sheltered in the central cavity in the header l l.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a discharge device, the combination with a discharge envelope having a reentrant wall area and an opposed cathode surfaced with reactive metal, of a charge adjacent said reentrant wall area which yields alkali metal vapor under heat, and a dished cover enclosing said charge between the same and said reentrant wall area, while permitting escape of matter outward from between them, the margin of said cover extending outward and rearward toward the envelope wall around said reentrant area.

2. In a discharge device, the combination with a discharge envelope having an internally recessed sheet metal Wall and an opposed cathode surfaced with reactive metal, of a charge in said recess which yields alkali metal vapor under heat,

and a sheet metal cover covering over said charge and said recess and welded to said cover at the edge of the recess, but permitting escape of matter outward from the periphery of the recess where it is unattached to the metal Wall.

3. In a discharge device, the combination with. a discharge envelope having an internally recessed sheet metal Wall and an opposed cathode surfaced with reactive metal, of a charge in said; recess which yields alkali metal vapor under heat, a sheet metal cover covering over said charge and said recess and welded to said cover at the edge of the recess, but permitting escape of matter outward from the periphery of the recess Where it is unattaehed to the metal wall, and means also carried by said metal wall for deflecting away from said cathode matter escaping as aforesaid.

4. In a discharge device, the combination with a discharge envelope comprising a vitreous tube with a sheet metal cathode header sealed to one end thereof, of a sheet metal anode header sealed to the other end of said tube and having a reentrant Wall area, a charge adjacent said reentrant wall area which yields alkali metal vapor under heat, and dished sheet metal cover welded to said anode header at the edge of its said reentrant Wall area and enclosing said charge, but permitting escape of matter outward from said area Where it is unattached thereto, the margin of said cover extending outward and rearward toward said header around said area.

HARRY L. LOUDEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,701,751 Foulke Feb. 12, 1929 2,067,817 Beggs Jan. 12, 1937 2,082,851 Smith June 8, 1937 2,117,735 Lester May 12, 1938 

